Traditional glass manufacture requires very high temperatures which preclude adding organic compounds to the glass structure or maintaining elements in their metallic or partially reduced states. The long homogenization times at high temperature normally used in traditional glass manufacturing also make difficult the retention of compounds or elements having high vapor pressures within a glass structure. Also, traditional glass manufacturing requires that any dopant compound or element used must be mixed in the starting batch.
Consequently, it is often difficult to achieve homogeneity on a molecular scale using traditional glass melting procedures, and it is nearly impossible to produce controlled gradients of additives or dopants. Moreover, it is necessary to clean the melting and forming equipment after processing each composition of glass made by traditional methods in order to avoid contamination of subsequent compositions. Consequently, the size of a production run must be quite large in order to be economical. Furthermore, the addition of multiple dopants in traditional glasses is restricted because the dopants often chemically interact with each other, with the glass matrix and even with the crucible itself at these high temperatures.
All of the above complications, which are typically encountered in the doping of glass compositions, are dramatically increased when the glass is pure silica because the melting point of pure silica is 1713.degree. C. and temperatures of 2000.degree. C. are often required to process the pure silica glass.